Metal extrusion presses are known in the art, and are used for forming extruded metal products having cross-sectional shapes that generally conform to the shape of the extrusion dies used. A typical metal extrusion press comprises a generally cylindrical container having an outer mantle and an inner tubular liner. The container serves as a temperature controlled enclosure for a billet during extrusion. An extrusion ram is positioned adjacent one end of the container. The end of the extrusion ram abuts a dummy block, which in turn abuts the billet allowing the billet to be advanced through the container. An extrusion die is positioned adjacent the opposite end of the container.
During operation, once the billet is heated to a desired extrusion temperature (typically 800-900° F. for aluminum), it is delivered to the extrusion press. The extrusion ram and dummy block are then advanced, so as to push the billet through the container and towards the extrusion die. Under the pressure exerted by the advancing extrusion ram and dummy block, the billet is extruded through the profile provided in the extrusion die until all or most of the billet material is pushed out of the container, resulting in the extruded product.
Dummy blocks for extrusion presses have been previously described. For example, U.S. Pat. No. 5,918,498 to Robbins discloses a dummy block having a dummy block base, a connector for connecting the dummy block base to a stem of an extruder, a replaceable wear ring connected to a forward circumferential portion of the dummy block base, a device for releasably securing the wear ring to the dummy block base, and a device for expanding the ring to engage an inside wall of a container of an extrusion press during extrusion. The wear ring is a metal collar having a conical interior surface converging towards the dummy block base. The device for expanding the ring comprises a metal plunger having a plunger head with a conical surface for engaging the collar conical surface to expand the collar as the plunger head is forced into the collar during extrusion. The converging surfaces of the collar and the plunger head extend a sufficient distance to permit telescoping of the plunger head into the collar to an extent whereby the collar is expanded to engage the inside wall of the container.
Improvements are generally desired. It is therefore an object at least to provide a novel dummy block for an extrusion press.